The invention relates to evaluation of core stack pressure.
When machine stator or rotor laminations become loose, the laminations vibrate. Lamination vibrations can damage machine lamination and winding insulation.
Conventional testing for inadequate core stack pressure involves attempting to insert a knife blade between adjacent laminations in a core stack, and, if the knife blade fits, determining that the core stack pressure is likely not sufficient. Typically pressures below the range of about 250 pounds per square inch (psi) (1724 kilonewton per meters squared xe2x88x92k N/m2) to about 350 psi (2413 k N/m2) fail the knife blade test. Several limitations of the knife blade test are imprecision (because the technique is qualitative and based on a pass-fail test) and the potential for lamination insulation damage.
It would be desirable to have an evaluation method that does not require inserting a knife blade between adjacent laminations of the core.
Briefly, in accordance with one embodiment of the present invention, a method for evaluating core stack pressure comprises: positioning a magnetic yoke near the core, the magnetic yoke being wound by an excitation winding; supplying current to the excitation winding to inject magnetic flux into the core; measuring a signal resulting from the injected magnetic flux; and using the measured signal to evaluate the core stack pressure.
In accordance with another embodiment of the present invention, a system for evaluating core stack pressure comprises: at least one magnetic yoke wound by an excitation winding for being positioned near at least one tooth of the core; a current supply for supplying current to the excitation winding to inject magnetic flux into at least one tooth of the core; a sensor for measuring a signal resulting from the injected magnetic flux; and a computer for using the measured signal to evaluate core stack pressure.
In accordance with another embodiment of the present invention a system for evaluating core stack pressure comprising: at least one magnetic yoke wound by an excitation winding for being positioned near at least one tooth of the core; means for supplying current to the excitation winding to inject magnetic flux into the at least one tooth of the core; means for measuring a signal resulting from the injected magnetic flux; and means for using the measured signal to evaluate core stack pressure.